Oxygen gas-sensing properties in dc conductivity of a semiconductive glass in the system V₂O₅-SrO-Sb₂O₃ with a composition V₂O₅:SrO:Sb₂O₃=73:18:9 (mol%) were investigated in flowing oxygen and argon gases at temperatures between 433 and 439K. The conductivity was lower in O₂ and higher in Ar than that in air. This was attributable to changes in the concentration of V⁴⁺ ion as a function of oxygen partial pressure. Changes in conductivity by switching the flowing atmosphere between O₂ and Ar gases were found to be reproducible. Sensitivity of 4.5 (433K) was obtained to 100% oxygen. The dynamic changes in conductivity by switching the flowing atmospheres were well explained by an oxygen diffusion and desorption model.

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TiB₂-dispersed B₄C ceramics were fabricated by reaction sintering of B₄C and TiC powders. The microstructure of this composite was observed mainly by transmission electron microscopy. TiB₂ particles dispersed uniformly in the boundaries of B₄C matrix. The interfaces of B₄C-B₄C, TiB₂-TiB₂ and B₄C-TiB₂ connect directly without intergranular phase, defect and impurity, and have no preferred orientation. However, “ribbon-like structure” carbon layer sometimes precipitates at B₄C-B₄C, TiB₂-TiB₂ and B₄C-TiB₂ interfaces, which form in parallel to (002) plane of carbon. The degradation of bending strength and the constant fracture toughness observed in the composites containing more than 20vol% TiC in starting material are caused by the increase of carbon precipitation.

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YBa₂(Cu_1-xAg_x)₄O₈ (x<0.1) superconductor was synthesized under high oxygen partial pressures by oxygen hot isostatic press. From Raman scattering spectroscopy, the phonon frequency of O(4)-Cu(1) stretching vibration increased and that of O(1)-Cu(1) vibration decreased by doping silver. Phonon frequency change is due to an increase in the force constant of O(4)-Cu(1) bond and to a decrease in the force constant of O(1)-Cu(1) bond by a silver replacement into the Cu(1) site. Ag-O bondings are detected in the 124 phase by an infrared absorption spectroscopy also. The evidence of silver replacement into Cu(1) site in YBa₂Cu₄O₈ was presented for the first time.

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The effects of addition of poly (ethylene glycol) (PEG), to gel films on the optical properties and structure of the resultant SiO₂ coating films have been studied before and after being subjected to an environment of high temperature and high humidity. The larger amount and the larger molecular weight of PEG produced the larger volume of pores in the resultant SiO₂ films on the decomposition of PEG during the heat-treatment. The refractive index of such porous films was found to increase due to water adsorbed in the films. On the other hand, the porosity and the amount of adsorbed water of the films decreased after the treatment in an environment of high temperature and high humidity. The decreases in porosity and the amount of adsorbed water were more significant in the films prepared with the addition of the larger amount of PEG with a larger molecular weight. These findings can be ascribed to the decrease in silanol groups and densification of the films with the treatment at high temperature and high humidity, as confirmed by the changes in IR absorption spectra and the results of TEM observation.

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Homogeneous, thick silica films composed of fine particles were prepared in a short time by using an electrophoretic deposition technique combined with the sol-gel method. Electrophoretic deposition was carried out using the silica sols derived from tetraethoxysilane hydrolyzed with water of a variety of pH; EtOH, i-PrOH, and n-PrOH were used as a solvent. In the case of pH=11.7 and a solvent of EtOH, the maximum coating weight was attained at an applied voltage of 140V and the thickness of the film was about 17μm. The surface of this coating film was found to be homogeneous and smooth by SEM observation. The coating weight was roughly proportional to the charge density with nearly the same slope independent of the kind of solvents.

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Silicon nitride, AlN polytype, YAP-phase, YAG-phase, Precipitation, Cooling rate, Anomalous microstructureWhen AlN-polytype (21R) powder is used as an additive to sinter Si₃N₄ ceramics together with Al₂O₃ and Y₂O₃ additives, anomalous black spots are found. These black spots contain β-Si₃N₄ and YAG-phase, i.e., garnet type crystal structure consisting of 5Al₂O₃⋅3Y₂O₃. The matrix contains also β-Si₃N₄ with addition of YAP-phase, i.e., perovskite type crystal structure with equal molar amount of Al₂O₃ and Y₂O₃. The different precipitated crystals in the black spots and in the matrix cause the dissimilarity of the appearance of the two regions. The YAG-phase nucleates at Fe inclusions which play a role as an embryo, and forms black spots. YAP-phase simply precipitates in the matrix by cooling the Si₃N₄ ceramics. To reduce the amount of the black spots, it is necessary to eliminate the Fe contamination which normally origins from raw powder production or milling processes.

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An aqueous slip of powder mixture of alumina and zirconia was formed by centrifugal casting. The viscosity of a concentrated slip, exhibiting rheopexy fluid behavior with complete deflocculation, was 1735.2mPa⋅s. The relative density of the body formed from the slip was 61.8%, i.e., 3.11g/cm³. The bending strength of the sintered body was 145kgf/mm². SEM observation and hardness measurements for a sintered body revealed no separation between zirconia and alumina particles. Centrifugal casting enables us to form a uniform alumina-zirconia composite ceramic body with high density, irrespective of the density difference between each one.

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Four kinds of silicon nitride ceramics with different grain sizes and different amounts of the boundary phase were prepared, and the polished surface of the samples was indented with a round diamond indenter. The morphology of the surface deformation, cracks and the structure under the indented surface were investigated. After indentation, a round impression was formed on the surface and the swelling was found around the impression. The diameter and the maximum depth of the impression were larger in the samples with a large grain size and a large amount of the boundary phase. Two types of cracks were observed, namely a radial crack and a Hertzian crack. The radial crack propagated from the impression above the indentation load of 147N, and its length was larger in the samples with a coarse grain size. The Hertzian crack was found inside the impression of the samples with a fine grain size. After etching in a NaOH melt a ring shape area was corroded away from the indented samples. The area of the corroded region depended on the grain size and the amount of the boundary phase.

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Effects of addition timing of dispersant on the slurry viscosity and various properties of slip cast bodies were examined. The dispersant was added during grinding with an agitation bead mill or after grinding. The addition during grinding was more effective in decreasing the slurry viscosity and in increasing the density of slip cast bodies. These effects were caused by the difference in the adsorbed state of the dispersant. With addition after grinding, the dispersant adsorbed on the powder was apt to be detached, while with addition during grinding, the amount of dispersant desorbed during subsequent processing was much smaller, presumably due to the stronger and irreversible adsorption immediately after the creation of active centers on the substrate surface.

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The effect of zirconia on crystallization of glasses with lepidolite composition and properties of glass-ceramics obtained have been investigated. The batches of 7LiF⋅15KF⋅28Al₂O₃⋅50SiO₂ (wt%) were melted at 1500°C for 10min and the melts were quenched by pressing the melt with platinum plate. The obtained glasses were heated at a constant heating rate, and the precipitated crystals were found to be lepidolite and β-eucryptite by X-ray diffraction analysis. The crystallization temperatures of lepidolite and β-eucryptite were 600 and 800°C, respectively at the heating rate of 10°C⋅min^-1. However, in order to precipitate the lepidolite in the glass containing no ZrO₂ by isothermal heat-treatment, the crystallization of lepidolite required heating the glass at 500°C for more than 1h. One percent ZrO₂ was sufficient for the crystallization of lepidolite. The activation energy for crystal growth of the glass was 268kJ/mol. The thermal conductivity of glass-ceramics heated at 500°C for 1h and then 800°C for 2h was 0.033W/cm⋅°C, which was larger than lepidolite glass-ceramics, and its thermal expansion coefficient and dielectric properties were similar to those of lepidolite glass-ceramics.

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Static fatigue, cyclic fatigue and constant stress rate tests were carried out at 1200°C in nitrogen atmosphere for toughened silicon nitride exhibiting a significant rising R-curve. The R-curves both in static and cyclic loading conditions were determined with measuring crack advance and fracture strength, in order to evaluate cyclic loading effects. The K_R value under a static loading condition increases as a crack advances and it reaches 12.5MPa⋅m^1/2 at the crack advance greater than 1.5mm. On the contrary, the K_R value under cyclic loads increases with advancing a crack and it reaches 9.5MPa⋅m^1/2 when the crack advances greater than 1.2mm. This different R-curve behavior suggests that bridging grains responsible for the toughening are damaged with the cyclic loads, resulting in a decrease in the maximum K_R value. Applying a Dugdale model to the bridging stress analysis, the bridging stresses under static and cyclic loading conditions were determined 100MPa and 65MPa, respectively.

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This paper reports the results of work on PZT/polymer 1-3 connectivity composites for solid ultrasonic applications, especially for AE transducers, in non-destructive inspection. A high sensitivity AE transducer employing PZT/polymer 1-3 composite was developed. Type 1-3 composite was fabricated using a “cutting and filling” technique: a poled PZT disk was cut into a large number of small rods. The inter rods spaces were then filled with polyurethane. For the evaluation of piezoelectric characteristics, composites with 40vol% PZT were made with values of g₃₃ four times large than the solid PZT values. The AE transducer had a higher sensitivity than a conventional type AE transducer.

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Thin films of the InN and In₂O₃ mixture system were deposited on α-Al₂O₃ (0001) substrates by reactive evaporation in mixed nitrogen-oxygen RF plasma. Crystal structure and electrical and optical properties of the obtained films were studied on films containing various amounts of nitrogen and oxygen. C-axis oriented InN thin films were obtained at mixing ratio of oxygen under 5%, and (111) oriented In₂O₃ thin films were obtained at mixing ratio of oxygen above 20%. Carrier densities of the films having InN increased as nitrogen content decreased and oxygen content increased. Resistivities of the prepared InN-In₂O₃ thin films varied from 10^-4Ω⋅cm to about 1Ω⋅cm, and band gap energies of them varied from 1.9 to 3.7eV.

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Polycrystalline pellets of Li₂Ti₃O₇ with the ramsdellite-type structure and Li₄Ti₅O₁₂ with the spinel-type structure were prepared by solid state reaction of Li₂CO₃ and TiO₂. The temperature dependence and annealing effect of Li⁺ ion conductivity were examined by the complex impedance technique. The conductivity of Li₂Ti₃O₇ decreased due to transformation of the ramsdellite phase to the hexagonal phase during annealing. A break was observed at about 350°C in the Arrhenius conductivity plot of Li₄Ti₅O₁₂. The conductivity of Li₄Ti₅O₁₂ was lower than that of Li₂Ti₃O₇, but remained unchanged during annealing. The conduction mechanism of Li⁺ ion through the spinel structure was discussed based on the ratio of bottleneck radius to Li⁺ ion radius, and a conduction path was proposed to be 8a→16c→8a positions.

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Strengthening of alpha-alumina-containing porcelain bodies was investigated by lamination with different compositions by two techniques. One was coating technique, in which the test bars were dip-coated with slurry of different batches, containing less amount of alpha-alumina. Coating caused an increase in bending strength of 24% with adequate coating thickness. Nevertheless, a formation of a crack at the surface led to a decrease in strength remarkably if the surface layer exceeded a critical thickness. The other was “double slip casting” technique, laminated bodies were made from two batches designated as surface and internal layers by sequential slip casting. Double slip casting yielded thick surface layer without any crack, thus substitution of zircon for alumina at the surface layer increased the mean bending strength from 38 to 44kgf/mm² and Weibull modulus from 6 to 17.

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As a material with low thermal conductivity for ceramic heat insulated engines, reaction-bonded Si₃N₄ (RBSN) was thought to be promising. In order to reduce the thermal conductivity, RBSN composites were fabricated from Si and several kinds of oxides, and then their thermal conductivities and microstructures were investigated. It was shown that (1) Al₂TiO₅ was the most effective additive to reduce the thermal conductivity of RBSN and that the value showed a minimum of 2.6W/m⋅K at 35wt% of Al₂TiO₅ content, (2) during sintering, Al₂TiO₅ decomposed and new phases formed multi phases in second phase in the sintered body, (3) temperature dependence of thermal conductivity decreased with increasing addition of Al₂TiO₅.

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A complex alkoxide, a precursor of Pb(Mg_1/3Nb_2/3)O₃, was synthesized using Pb(OAc)₂, Nb(OEt)₅ and Mg as starting materials. The chemical structure of the complex alkoxide was described on the basis of the change in solubility in organic solvents, and IR and Raman spectra. The crystallization behavior of the hydrolysis product was examined. The complex alkoxide is assumed to be a polymer produced by ester-exchange reaction of Pb(OAc)₂ and Nb(OEt)₅, in which Mg atoms are coordinated to acetoxy groups (CH₃COO-). The powder was prepared by hydrolysis of the complex alkoxide with aqueous ammonia in the present of acetone. The powder crystallized to the perovskite phase at 300°C with a 70% yield, but a pyrochlore coexisted. These result probably reflected the chemical structure of the precursor powder obtained.

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The effect of moisture content of granules on green and sintered bodies of alumina ceramics was studied. Alumina green bodies were formed from spray-dried granules containing 0.1-2.0% moisture at 50-350MPa and sintered at 1600°C for 2h. Their microstructures were examined with an SEM and an optical microscope of transmission mode. The moisture content of granules significantly affected properties of green and sintered bodies. With increasing moisture content of granules, the density of green bodies increased. Fracture mode of green bodies changed from inter-granule to trans-granule. The Weibull modulus of sintered bodies increased with increasing moisture content of granules.

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A new version of the Rietveld-refinement program RIETAN has been developed for the analysis of angle-dispersive X-ray and neutron powder diffraction data. It has several features such as the modified pseudo-Voigt function of Thompson, Cox and Hastings, representation of peak asymmetry by a multi-term Simpson's rule integration, the March-Dollase function to correct for preferred orientation, and a background function consisting of Legendre polynomials. Powder diffraction data of four inorganic compounds were analyzed with this program to test its effectiveness. In all the refinements, the new version of RIETAN gave lower R factors than the old one. The result of Rietveld refinement for anatase-type Ti_0.85Sn_0.15O₂ showed that the model function implemented in the new program well fits its X-ray powder diffraction pattern exhibiting anisotropic strain broadening.

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A new processing method for solidifying pulverized concrete wastes is presented. The objective of this study was to develop a technology to recycle concrete wastes. Concrete wastes were pulverized and then solidified by a hydrothermal hot-pressing method, which is a press-forming technique under hydrothermal conditions using an autoclave. The reaction temperature was in the range of 120 to 300°C, and the reaction time was in the range of 10 to 40min. The tensile strength of the solidified concrete waste was determined by a Brazilian test. It was shown that concrete waste can be solidified under the above reaction conditions. The measured tensile strength increased with increasing temperature, and a steep increase was observed at the reaction temperatures of 150 to 200°C. The tensile strength of 5MPa was achieved above 200°C. The steep increase in the tensile strength was shown to be due to the formation of tobermorite.

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